Stackable basket



FIG. 1 is a side elevational view of the design;

FIG. 2 is a front elevational view of the design;

FIG. 3 is a rear elevational view of the design;

FIG. 4 is a top plan view of the design; and,

FIG. 5 is a bottom plan view of the design. 

The ornamental design for a stackable basket, as shown and described. 